Replacement Billet Head Domes for Polaris (800 / 850 / Boost / 9R)

Primary Application: Polaris 800 Cleanfire, Patriot 850, Patriot Boost, and Patriot 9R / 900 Big Bore snowmobiles equipped with a Bikeman Performance Modular Billet Head.

Dial in your engine’s compression ratio for peak horsepower across changing riding conditions with Bikeman Performance Replacement Billet Head Domes for Polaris snowmobiles. Designed to drop directly into Bikeman modular billet cylinder head shells, these interchangeable domes allow you to rapidly alter combustion chamber volume to suit changing mountain elevations, high-octane race fuels, or low-elevation pump gas setups without purchasing an entirely new head assembly.

Each dome is CNC-machined from aircraft-grade billet aluminum with Bikeman’s custom squish band profile and combustion chamber geometry. This precision design promotes rapid, uniform flame propagation, drops engine operating temperatures, and delivers superior detonation (DET) suppression during sustained, high-load pulls.

Key Performance Features

• Modular Compression Tuning: Easily swap domes to adapt your machine for low-elevation trail riding, high-altitude mountain trips, or race fuel configurations.
• Optimized Combustion Geometry: Engineered with proprietary squish band angles and chamber volumes to maximize horsepower output while eliminating detonation hot spots.
• Superior DET Suppression: Redesigned chamber profiles keep cylinder pressures stable and prevent automated ECU power derating and limp mode.
• Precision CNC-Machined: Crafted from high-grade billet aluminum for exact volume consistency across both cylinders and rapid thermal dissipation.
• Direct Drop-In Fitment: Precision engineered exclusively for Bikeman Performance Polaris Billet Head shells using factory O-ring seals.

Available Dome Options & Specifications

Select your engine configuration and dome part number from the dropdown menu above:

Polaris 800 Cleanfire Domes (Fits Bikeman 04-311 Head Shell)

• Low Altitude 41cc (Part #: 04-311-800-41): Calibrated for 0–5,000 ft elevation on 91+ premium pump gas.
• High Altitude 37.5cc (Part #: 04-311-800-37.5): Calibrated for 5,000+ ft mountain elevations on 91+ premium pump gas.

Polaris Patriot 850 Domes (Fits Bikeman 04-318 Head Shell)

• Low Altitude / Pump Gas (40.5cc / 11.8:1 Comp) [Part #: 04-318-850-40.5]: Calibrated for 0–5,000 ft elevation on 91+ premium pump gas.
• High Altitude / Pump Gas (36.5cc / 12.5:1 Comp) [Part #: 04-318-850-36.5]: Calibrated for 5,000+ ft mountain riding on 91+ premium pump gas (or low-altitude race gas setups).

Polaris Patriot 850 Boost Domes (Fits Bikeman 04-318 Head Shell)

• Pump Gas 43cc (Part #: 04-318-850-43): Optimized combustion volume and squish band tailored specifically for turbocharged Patriot Boost applications on 91+ pump gas.

Polaris Patriot 900 / 9R / Big Bore Domes (Fits Bikeman 04-318 Head Shell)

• Pump Gas 42cc (Part #: 04-318-900-42): Safe, reliable compression for all elevations (0–12,000 ft) on 91+ premium pump gas.
• Race Fuel 37cc (Part #: 04-318-900-37): High-compression race profile. Requires 110 octane fuel (100% race gas from 0–6,500 ft; 30% blend above 6,500 ft).
• Race Gas Low Alt 45cc (Part #: 04-318-900-45): Custom low-altitude race fuel calibration dome.
• Race Gas Low Alt 47cc (Part #: 04-318-900-47): Custom low-altitude race fuel calibration dome.
• Race Gas Low Alt 49cc (Part #: 04-318-900-49): Custom low-altitude race fuel calibration dome.
• Race Gas Low Alt 51cc (Part #: 04-318-900-51): Custom low-altitude race fuel calibration dome.